This invention relates to a modular motorized wheel hub for bicycles, scooters, golf carts and other on and off road vehicles. It relates more particularly to a compact electric modular motor/wheel hub assembly which develops sufficient torque to power a variety of vehicles.
There are numerous vehicles in use today which have battery-powered electric motors to drive the wheels of the vehicle. These include bicycles, adult tricycles, wheel chairs, motor scooters, golf carts, all terrain vehicles, etc. In many such vehicles, the motor is mounted to the vehicle frame with the motor output being coupled to the wheels by way of a chain drive, gear train or the like.
There also exist in the prior art various bicycles which have an electric motor connected directly to a wheel hub and arranged to rotate that hub. In some cases, the motor is mounted outside the wheel hub and takes up considerable space; see e.g., U.S. Pat. No. 5,622,187. These are not modular assemblies. In other instances, the motor takes the place of the usual wheel hub and rotates the rim of wheel; see, e.g., U.S. Pat. Nos. 552,271; 5,272,938; 5,341,892 and 5,581,136. Such motors are also relatively large, occupying a large percentage of the area within the associated wheel rim.
There do exist a few examples of bicycle-type vehicles whose motor is located entirely within the hub of the wheel; see e.g., U.S. Pat. Nos. 572,036; 2,514,460 and 3,921,741. As to these, in some cases the hub assembly is overly wide so that it cannot be mounted to the fork of a conventional bicycle frame. In other cases, the assembly is composed of a multiplicity of separate parts which are difficult to make and do not assemble as one unit. However, the most serious disadvantage of prior motorized hub assemblies of this general type is that they tend to overheat when used for a prolonged period as the bicycle""s or other vehicle""s sole source of power. In other words, while those prior assemblies may operate satisfactorily as a power assist device, when used alone to drive the vehicle, they either consume too much power and drain the associated battery after only a relatively short time or they do not develop sufficient torque to enable the vehicle to travel at a sufficient speed particularly on upgrades.
Accordingly, it is an object of the present invention to provide an improved modular motorized wheel hub assembly for bicycles and other vehicles.
Another object of the invention is to provide a modular motorized hub assembly of this type which is comparable in length and diameter to a conventional non-motorized wheel hub.
A further object of the invention is to provide such a modular assembly which is composed of a minimum number of separate parts which can be assembled as one unit without requiring any special tools or other equipment.
Another object of the invention is to provide a modular motorized hub assembly which provides a high torque output in a compact package and allows use of a high speed motor to minimize the package size and weight.
A further object of the invention is to provide a motorized wheel hub assembly which does not become overheated in use.
A further object of the invention is to provide a modular motorized wheel hub assembly which has extremely high efficiency over a wide range of speeds.
Another object of the invention is to provide such an assembly which can also function as a motor generator to recharge the assembly""s DC power source and provide a controllable electric vehicle brake.
A further object of this invention is to provide a controllable electric hub assembly of this type having an absolute minimum number of electrical conductors that have to be brought to outside connectors to allow all of them to pass through a small central shaft of the assembly.
Another object is to provide such a motorized hub assembly which is especially suited for powering a small urban vehicle or even a boat propeller so as to provide high torque at low speed and lower torque at high speed.
Other objects will, in part, be obvious and will, in part, appear hereinafter.
The invention accordingly comprises the features of construction, combination of elements and arrangement of parts which will be exemplified in the following detailed description, and the scope of the invention will be indicated in the claims.
In general, my assembly comprises modular DC electric motor incorporated into a wheel hub having stationary collinear shafts projecting from opposite ends of the hub. The motor stator is mounted inside a stationary stator case or shell inside the hub which case is connected to one of the shafts. Planet gears comprising a gear reducer are rotatably mounted to the case which gears mesh with a ring gear formed on the inside wall of the hub. These planet gears are rotated by a small diameter sun gear or pinion which rotates with a motor rotor positioned within the stator. Electrical connections to the stator are made through one of the shafts by which power may be provided to the stator causing the rotor to rotate. The rotor turns the pinion which then rotates the planet gears causing the hub to rotate relative to the shafts which are fixed in use.
A sprocket with a one-way clutch may be incorporated into the hub assembly so that if the motor rotates the hub faster then the sprocket is rotated (as on a power-assisted bicycle), the sprocket will free wheel. In addition, if the associated wheel is braked or raised from the ground and rotated manually, the motor can function as a generator to recharge the batteries that power the motor.
The hub is sealed from the atmosphere and internal lubrication channels are provided for circulating a fluid which transfers heat from the motor in the stator case and the gear reducer to the hub where it is conducted to the outside thereby allowing the motor to operate with a high torque output for a prolonged period without overheating.
The motor is basically a high performance, variable speed, brushless, sensorless, internally cooled, three-phase, computer balanced motor/generator with extremely wide band efficiencies approaching 95% with 90% efficiency down to and below 20% maximum speed. This high performance motor is married to an unusually small very efficient planetary gear reducer resulting in an unusually compact motorized hub assembly for a vehicle.
As will be seen later, the modular assembly is composed of a minimum number of parts which are relatively easy to make and to put together as one unit. Therefore, the assembly should be economical to make in quantity.